Shock absorber



Dec. 1, 1931. M. TIBBETTS SHOCK ABSORBER Filed 1m. 16. 1,927

r A x M Patented Dec. 1, 1931 ED PA MILTON TIBBETTS, OEDE TROIT, MICHIGAN, ASSIGNOR T PACKARD MOTOR OAR/COM- IPANY, OF DETROIT, MICHIGAN, A CORPORATION OF MICHIGAN snock ABSORBER Application filed December 1e,', 1927. Serial No. 240,662

This invention relates to' motor vehicles and particularly to shock absorbers'of the-hythe piston,the pressure ofthe liquid'depen'ding uponthe shock being absorbed. The area of the by-pass around the piston is ordinarily controlled by; somevalve device such by pass from the outside of theabsorber casing, and the needle valve is'rather elaborately packed near its outside end to prevent leakage from the absorbercasing around the needle valve. But due 'to the' pressure at which the liquid is bv-pa'ssed, the pressure reaching at times as high 'asBQOO pounds per square inch, even .themost elaborate formof' packing will not entirely preventfleakage around the needle valve. I v e An obiect of the present invention is to provide a hydraulic shock absorber with means to preventleakage of the liquid therefrom around the bv-pass needle valve. Another object of the invention is to reduce the pressure of the"by-passed liquid around the by-pass needle-valve of. a hydraulic shock absorber. i 1 f 7 Another objectiofithe invention is. to obviate the V necessity for an elaborate packing around the by-p'alssneedlevalvefofi a hy: draulic shockabsorber. I i Other objects of the invention willj appear from the following description taken in con 4Q nection with'the drawings whichrforma'part of this specification, and in which? Fig.1 is a sectional viewof' a shock absorber embodying invention, the section being substantially on lined- 1 of Fig.2;

Fig. 2 is a section through the shookab- Fig; 3 is an enlarged detail view illustrat ing the needle valve employed in the shock absorber of "the present invention, and

as a needle valve'mounted in position in 'the i p absorber to 'form an auxlliariy 'Fig. 4 isan enlarged sectional view sub stantiallyjon line H of Fig. 1.

Referring to the drawings, 10 is the body or casing of the shock absorber having 8 I cylindricalportion 11, an end wall 12 and a bearing portion 13. The cylindrical por tion and end wall are machined intern'all to form a working chamber 1 1 for the shocli absorber.v A cover 15 is fitted over the opefn I end of the casing and is ,secured thereto by numerous bolts 16. The cover 15 has an extension 17 fitting into the cylindrical portion llof the casing, the extension cooperate ing with the body orcasing of the shock reserve tank 18. A suitable lling opening (not shown) is provided and both the work; ing chamberiand the reserve tank are sub stantially filled with any suitableliquid suc as oil or glycerine. 7

A iston19 mounted to oscillate in the worklng chamber 14 has a shaft 20 suitably supported in the casing and cover. A packreservoir or ing 21 is compressed against bearin sleeve 22 by ahollow nut 23 screwed on the earing portion 13 of the casing. Outwardly'of nut '23 an arm 24 is keyed or otherwise suitably connected to the shaft 20 and is held thereon by nut25 and lock washer 26. The shock absorber is shown mountedupon a support 27 by means. of twoclarge bolts 28 extending through suitable openings in the casing and cover. 'Arm 24 is adapted for connection in any suitable manner to a part which moves relatively to the support 27 so that piston 19 will be operated in the working chamber as the vehicle parts move relatively to each other. To permit arm 24 'to operate with somewhat less resistance when moving in one direction than in the other, piston 19 is .provided fwith acheck valve (not shown) which permits liquid in the workingchamber to pass relatively freely through the piston in one direction, but doesjnot permit the y o A, V liquid to pass through in the other direction. sorber taken substantl'ally'on l he 2'7201? I Provisionis made for by-passing some of the liquid' equally'on both strokes of the piston and in the shock absorber shown, this by-pass means is in both the piston "and shaft; Shaft 20 is drilled from its outer end inwardly providing an opening 29 that extends through the zone of the piston. Two

- relatively small radial passages 30 and 31,

hereinafter termed high pressure passages, connect with opening 29 and extend to opposite sides of the piston and a relatively v largepassage 32, hereinafter termed a low pressure passage, extends through piston 19 and connects'opening 29 with the workingzehamber on opposite-sides of'thepiston through short passages 33 and 34 in the piston having substantially the same crosssectional area as the low pressure passage:

32. Suitable check valves 35 and 36 cooperate with the short passages 33 and 34 sponding to the angle included between the high pressure passages 30and 31 and serve to connect these passages with lowfpressure passage 32.; The-cross-sejctional area of this connection may be varied by simply turning the needle valve up tighter in the shaft or backing it off. slightl aswill be apparent from Figs5'2'and4 of he drawings. a

Liquid by passed around the piston is forced at relatively high pressure into high pressure passage 30 or 31 depending upon the direction in which the piston is moving andis conductedthrough connectingpassage 41 or 42 in the head offlthe needle valve to the relatively large low pressure passage 32. Immediately upon entering low pressure passageg32the pressure of the liquid is released, due to the large space into which itis permitt'ed'toexpand', afterwhich it passes into the Working chamber on the receding side of the ;piston through passage 33Ior 34 and check valve 35 or 36. The 'liquid'is thus conducted through a by-pass having a-high pressure portioncomprising high pressure passage '30 or 31 and connecting passage 41 or 42 in the needle-valvehead, and a low pressure portion oomprisingrelatively large low pressure passage 32 and short passage-33 or 34. It will be noted that} low pressure passage 32 is preferably large enough to completely sur round needle valve headlO so that the pressure of the by-passed liquid will be reduced allv around the needle valve. "In addition to this,.-low pressure passage 32 is preferably placed intermediate the high "pressure .passages 3()..and 31 and the outside endoffthe needle valve to eliminate any possibility of leakage of the liquid around theneedle valve. inpther-wordssince the low pressure portion 32 of the by-pass is placed between the high pressure portion 30 or 31 and the outside end of the needle valve, the pressure of the liquidis reduced all around the needle valve at a considerable distance from the outside end of the needle valve and there is consequently no tendency .for the liquid to be forced out of the absorber around theineedlevalve. The necessity for the elaborate packing heretofore found necessary around the outer end ofithe Shy-pass needle :valve i's-thns obviated. jl'nplac'eofithe elaboratezpacking, the simplest for the-.elaborate vpacking heretofore required arounditlie outer end of such needle valve.

'It will be understood thatvarious forms oftheinviention other than those described above may be used without departing from the spirit or scope of-the invention.

Having .thusfdescribed my invention, what I. claim anddesire to secure by Letters Pat- .ent' :is: i a .L J'In a shock absorber, a. casing, a piston operable in-the casing,.-a 'by-pass comprising high; and low pressure passages connecting the interior of the casing on opposite sides of the piston and a needle valve .having'a portion extending outside of the casing providingcommunicationbetween' the high and low pressure passages, the low pressure passage beingpositioned inter-mediate thehigh pressure passage and that portionof the needle valve extending outside of thecasing.

2.Ina shock-absorber, a casing, a piston operable in the casing, a bypass connecting opposite-sides of the piston, theby-pass having both high. and;l0w pressure-passages and a. needle valve extending through the low .pressune passageand providing a connection between the high and low pressurepassages. 3.. Inrav shock. absorber, .-a casing, a piston operable in the casing,.a shaft for the piston, a-by-pass.conneotingopposite sides :of the piston comprising a: high pressure passage in the shaftand a .low pressure. passage in the piston and shaft and aneedle valve providing a' connection between the high and low pressure passages. I 7

4; Inzashock absorber, a' casing, a piston operable in the casing, and a by-pass connect ing opposite sides of 'the piston comprising a high pressure passage of'relatively small cross=sectional-area and .av low pressure passage of relatively large cross-sectional area connected together,

5. In a shock absorber, a casing, a piston operable in the casing, a by-pass connecting opposite sides of the piston comprising a high pressure passage and a low pressure passage and a needle valve providing a connection between the high and low pressure passages, said low pressure passage entirely surrounding a portion of the needle valve.

6. In a shock absorber, a casing, a liquid in the casing, a piston operable in the casing,

a shaft for the piston, by-pass means around the piston comprising a high pressure passage in the shaft and a low pressure passage in the piston and shaft, a needle valve mounted in the shaft and providing a connection between the high and low pressure passages and having a portion extending outside of the shaft, said low pressure passage being po-' sitioned intermediate the high pressure passage and the portion of the needlevalve ex tending outside of the shaft, said low presf sure passage entirely surrounding a portion of the needle valve.

7. In a shock absorber, a casing, a liquid in the casing, a pis on operable in the casing, and means including a valve member for bv-passing the liquid in the casing from one side of the piston to the other and for reducing the pressure of the liquid while passing through the by-pass, the valve member having passages forming a part of the bypass.

8. In a shock absorber, a casing, a liquid in the casing a piston operable in the casing, abv-pass around the piston and a needle valve for the by-pass, said by-pass being constructed with different cross sectional area to reduce the pressure of the by-passed liquid at adjacent portions of the needle valve.

In testimony whereof I affix my signaturev MILTON TIBBETTS 

